Common Powder Coating Faults and Solutions

Most Common Powder Coating Faults

1. Inclusions: Dust and Residue on Coated Surfaces

Inclusions are small particles, such as dust or residues, that remain visible on the surface of coated parts. These faults are typically caused by poor preparation of the components before coating. To avoid inclusions:

• Clean Components: Wipe parts with a lint-free cloth to remove dust and residues.

• Use Compressed Air: Blow off any remaining particles just before coating with a stream of compressed air.

Note: Welding splatter can sometimes be mistaken for inclusions. A quick test: scratch the area with a screwdriver. If the particles dislodge, they are inclusions. If they don’t, the issue is welding splatter, and feedback should be provided to the welders.

Solution: Spray anti-splatter solutions on areas to be welded to minimise splatter and reduce the risk of inclusion.

2. Uneven Coating: Causes and Prevention

Uneven coating typically occurs due to incorrect sprayer setup or improper gun operation. Here’s how to avoid this issue:

Sprayer Setup

• Ensure the gun is properly set up to disperse powder evenly. If too much powder is dispensed and not enough air is used to purge it, ‘surges’ of powder will accumulate in one area.

Gun Movement

• When coating intricate parts, the sprayer must move the gun in continuous motions. If the gun dwells on one area, it will apply an excessive amount of powder, leading to an ‘Orange Peel Effect’, which can make the coating look uneven and unsightly.

Solution: Regularly check gun settings and technique to ensure even powder distribution and avoid “orange peel” effects.

3. Areas Not Coated: How to Achieve Complete Coverage

In some cases, areas may not be fully coated, especially on intricate parts. These areas may appear to have powder applied, but they won’t fully cover the surface.

Solution: The sprayer should aim for repeatability—consistent movements and timings during spraying to ensure all parts are evenly coated. By applying the same amount of powder to each area, the result will be a more uniform finish.

4. Masking Errors: Ensuring Accurate Masking

Improper masking often occurs when the masking material isn’t applied according to the correct specifications. To ensure accurate masking:

• Use Detailed Drawings: Provide a drawing of the part, highlighting areas where powder coating should not be applied. This ensures the person in charge of masking knows precisely where to apply the masking material.

Solution: Always refer to clear masking instructions to avoid misapplication.

5. Under-Curing: Identifying and Preventing Coating Defects

Under-curing is hard to spot but can significantly affect the durability of the coating. Common signs of under-curing include:

• Glossy Appearance: If the coating looks overly glossy, it might be under-cured.

• Inconsistent Gloss: Heavier parts tend to be glossier than thinner ones.

Testing for Under-Curing

A simple test involves hitting the coated surface with a hammer. If the coating chips or separates from the substrate, it is likely under-cured.

Solution: Ensure parts are correctly cured according to the recommended time and temperature to achieve a durable, non-glossy finish.

Conclusion: Preventing Powder Coating Issues

By following these steps, you can minimise common powder coating faults like inclusions, uneven coatings, and under-curing. Always pay attention to preparation, application methods, and curing times to ensure a high-quality, durable finish. For more advice or to discuss a specific project, contact us today.